Mold for lens-mounting blocks.



W. W. ESSICK.

NoLD FOR LENS MOUNTING BLOCKS.

APPLICATION FILED IAN. I9. 1914. I

Patented June 22, 1915.

NNNNNNNN MYX/fam W 55mm,

'WILLIAM W. JESSICK, 0F REING, PENNSYLVANIA.

MOLD FOR LENS-MOUNTING BLOCKS.

Application led January 19, 1914i.

T0 all whom it may concern Be it known that ll, WILLIAM W. lEssIon, acitizen of the United States, residing at Beading, in the county ofBerks and State of Pennsylvania, have invented' certain new and useful`improvements in Molds for Lens-Mounting Blocks, of which the followingis a specification.

My invention relates particularly to lens grinding, and my objectbroadly is to provide for producing with great economy of laborand aminimum of special skill and judgment, lenses which will conform withextreme accuracy and uniformity to determined requirements.

lln the method of grinding commonly employed, a series of the roughlyshaped blanks are mounted upon the surface of a holder or block, and aresubjected to abrasive action by a corresponding grinder; the-holdingsurface of the block being commonly of a pitch composition to Which thelenses adhere as placed by the operator. ln

order to insure some degree of accuracy in thus mounting the blanks,facets have been formed on the holding surface to facilitate the properplacing of them; these facets being formed by correspondingly shapedmolds for the surfacing pitch composition. rllhe accuracy of themountingthen depends primarily upon the correctness and uniformity of thefacet-forming recesses in the mold, and also upon the accurate placingof the lenses upon the facets. lit Will be readily understood that avery slight variation in the facet-forming recesses, such for instanceas is apt to occur through Wear of a cutting tool; or a very slightmisplacing of the lens or blank relative to the focal axis; will resultin a more or less seriously defective lens.

. My invention provides for avoiding these defects by insuring theaccuracy of the lensmounting 4facets upon the holder and the accurateplacing of the blanks.

Figure l illustrates a lens holder or block in cross-section, with thepitch surfacing thereon; the facets to the right of the latter beingrepresented as adapted for mounting the flat blanks for the firstgrinding, and those to the left for remounting to grind the othersurface. Fig. 2 indicates a grinder employed therewith. Fig. 3 is a planview of my improved lens-block mold, a portion only of the facet-formingsegmenta being shown in position. '.Fi. t is a Specification of LettersPatent.

Patented J une 22, JlQJl. serial No. 312,925.

cross-section thereof on the line 4 4. Figs. 5 and 6 show one of thefacet-forming segments; Fig. 7 is a plan view of the mold therefor withthe coping portion removed; Fig. 8 is a cross-sectional view of thecomplete segment mold; and Fig. 9 shows separately the facet-formingportion thereof, modified in shape as required for producing avsecond-grind lens holder for convex spherical grinding. Figs. 10, 11,and 12 indicate modified forms adapted for cylindrical grinding.

'lhe holder or block 2 shown in Fig. l, is of convex vform adapted forconvexly grinding lenses; a similar concaved form being employed forconcave grinding as is Well understood. The pitch-surfacing 3 of theholder 2 is shaped on the completed correspondingly concaved mold Figs.3 and 4f, the novel construction of which is specifically described.

his improved mold as shown in Figs. 3 and 4, comprises a rigid shell orbacking l0, the spherically concaved surface 1l of which is accuratelyfinished to a curvature of greater radius than that of the holder 2 3,as determined by the thickness of the facetforming segmental lining withwhich it is provided. This lining is' made up of segments l5, l5, 15b,preferably arranged in circular series forming successive zones asindicated; the segments in each zone being exactly alike, but varying inoutline from those which form the other zones. rlhese zones are boundedby circles of increasing diameter, a I) c UZ as shown, to which theparallel ends 15, 15d of each segment conform, While its sides 15e, l5econverge to- Wardthe center 16 of the mold, as indicated in Figs. 3 and5. Fach of these segments is provided with a facet-forming recess l? asshown; and practically absolute accuracy of arrangement of theserelative to the focal center, which is an essential requirement, issecured by the use of segment forming molds such as is illustrated inFigs. 7, 8, and 9: the showing being specifically adapted for producinga series of the segments 15a illustrated in Figs. 5 and 6.

rlhis facet-forming segment mold comprises a base portion 20, a 4copingportion 21, and an interposed segment-Wall portion 22; Which portionsare formed as illustrated, with parallel spherically curved opposingsurfaces, 2].a of Which conforms accurately Withthe surface ll of themold'shell illustrated in l 10 so as to properly seat upon the latter.The base portion 20, as shown, is formed with a counterbored centralopening extending throughthe boss to which is adjustably fitted aseparate facet-forming mold portion 26, having a head 27 fitted to saidcounterbore, and an oval facet 28- on said head.

As shown in Fig. 8 this projecting oval facet 28 has aflat `face; Whilein Fig. 9 it is shown with a spherically concaved face; one or the otherof these being used according as the lens holder to be produced isintended for mounting unground blanks, or

such as have been already ground on one face to suchspherical curvature.In either case the shape and size of the facet is made to correspondwith the lens intended to be yseated thereon; and its face is accuratelycentered and squared to the radial line of the spherical curvature ofthe opposing surl faces of the mold portions 20, 21, and accuratelyspaced from said surfaces.V It will be readily understood thatpractically absolute accuracy-may be readily secured by suchconstruction, so when a series of like segments are .produced in themold and assembled in the mold shell 10 as indicated 1n Fig. 3, eachfacet will bey accurately located relative to the focal axis ofgrinding. ln arranging the mold preliminary to forming these segments,the facet-forming portion 26 may be-accurately adjusted in its openingso as to properly set the axial line 30 of the facet, as indicatedinFig. 7, the operation otherwise being obvious from the drawing. It willbe readily understoodalso that when two or more series of segments areemployed, arranged in different zones as indicated in Figs. 3 and'4, thewall portion 22 of the segment mold Will be correspondingly varied foreach series of segments Without varying the determined .uniform relationof the facets to the focal axes when the segments are properly assembledin the lens-holder molding shell 10 as indicated; and that thepitch-surfacing 3 of the lens-holder 2, as formed theifein, will providesimilarly ac-- curate lens-attaching facets. Y

The lens blanks which are attached to a holder having flat facets asshown'to the right of Fig. 1, may vary from the normal indicated at m,so as to require excessive' or unequal grinding,-as for instance theprismatic form of blank indicated vat y. This` like thickness with oneface convexly ground to the required curvature ,-as indicated at ato theleft of Fig. 1, where the lenses are shown mounted uponthe'corresponding concaved facets so as to properly expose the otherlfaceto the' second grinding process which results in the finished lensindicated at fw. Heretofore the rough-edged blanks have been mountedupon the lens-holders, and both faces ground before bevcling the edges;but I am enabled to double-bevel the edges first, making this bevelingtrue to one face of the lens regardless of the other as indicated at y,thus providing blanks of uniform shape and size so far as the flatmounting face y1 and the beveled edge is concerned, which greatlyfacilitates the accurate setting of the blanks upon the correspondinglyformed facets; any excess grinding required upon the exposed face, as onlens y, merely equalizing the edge beveling, and the final face grindingproducing a finished product which is not liable to be scratched orotherwise damaged as when the belveling of the edges is effected by asubsequent operation.

To further facilitate the proper placing of the lenses upon the facets,I preferably provide setting means consisting as indicated in Fig. 5 ofan oval guide'ridge 35 parallel with the rim of the facet. This 'toaccurately and quickly place the latter.

The ridge 35 is readily formed on the segment by means of acorresponding groove 35a provided in the segment mold (Fig. 7).

As indicated in Figs. 10, l1, and 12 my segmental lining may also beadvantageously j applied to forming other than spherical lens holders,though the need thereof in the latter case is considered to bepractically greater. As shown in these figures the base portiony 10 ofthe mold is cylindrically curved, and segments of corresponding form, asmade in a corres ondingly modified segment mold such as s own in Fig. 8,are fixed either to the cylindrically convexed or concaved surfaces asrequired; or such surface may obviously be made plane, withcorrespondingly formed lining .segments if fiat lenses are to beproduced,

or adapted for prismatic lenses if desired. After my improved segmentalmold has been thus built up in any required form, solid duplicatesthereof may be cast therefrom ofsuitable material and be similarly usedin molding like lens holders.

What I claim is 1. A lens-block mold comprising va spherially-surfacedbase portion, and a sectional facing for said spherical surface made upJ of separately formed facet-forming spherical segments the marginalportions of each of'whch abut adjacent segments.

2. A lens-block mold comprising a spherically-surfaced base portion, anda sectional facing for said spherical surface made up of separatelyformed facet-forming spherical segments arranged in a spherical zone,thc side Walls of each segment abutting adjacent segments.

i ci) zof 3. A lens-block mold comprising a spherically-surfaced baseportion, and a sectional facing for said spherical surface made up ofseparately formed facet-forming spherical segments arranged in zoneseries, the segments of each series being different in contour fromthose of each other sries substantially as set forth.

facet forming sphericalsegment mold comprising base and coping portions.providing parallel spherically-curved surfaces and one of whichisprovided with a facet-forming portion squared to a radial line of saidsurfaces, and segment walls between said surfaces inclosing saidfacetvforming portion.

, 5. A lfacet forming Yspherical segment mold comprising base and copingportions providing parallel spherically-curved suraces, a facet-formingfitting to one of said portions squared to a radial line of said sur;faces, and segment walls between said surfaces inclosing saidfacet-forming portion.

facet forming spherical segment moldcomprising base and coping portionsproviding parallel spherically-curved surfaces, an adjustablefacet-forming ttin'g to one ofsaid portions squared to a radial line ofsaid surfaces, and segment walls between said@ surfaces inclosing saidfacet-forming portion. l,

7. A facet forming providing parallel spherically-curved surfaces, andone of which is provided with a facet-forming portion squared to aradial line of said surfaces, and a segment-wall portlon fitted between1ysaid spherically curved surfaces.

spherical fsegment `mold cmprislng base and coping portions 8. A facetforming sphericalsegment mold comprising base and coping portionsproviding parallel spherically-curved surfaces, one of which is providedwith a facetforming portion squared to a radial line of said surfaces,and a segment-wall portion fitted between said spherically curvedsurfaces; said segment-wall portion having opposite parallel walls andconverging intersecting walls substantially as set forth.

9. A` lens-block mold having lens facets which are ridged to formlens-setting grooves.

10. A facet-forming segment mold comprising base and copingfportionsproviding opposing` surfaces, and segment-walls between said surfaces;one of said portions being provided with a lens facet which is formedwith a lens-setting groove.

11. A facet-forming segment mold comprising base and coping portionsproviding opposing surfaces, and segment-walls between said surfaces;one of said portions being provided witha lens facet.

12. A lens-block mold comprising a spherically-surfaced base portion,and a. sectional facing for said spherical surface made up of separatelyformed facet-forming spherical segments arranged in zone series, thesegments of each series being different in contour from those of eachother series, and the marginal portions of each segment abuttingadjacent segments.

In testimony whereof I affix my signature in presence of two witnesses.

WILLIAM W. ESSICK.

Witnesses:

D. M. STEWART, ADAM L. OTTERBEIN.

